I agree that you really could have stopped feeding a while ago. Spring feeding isn't supposed to provide their entire supply for the winter, but just to give them some fuel to use for drawing comb and to keep them going until they build up their forager numbers. Which it sounds like yours have!
Generally, I'd say feed a new package until they have some capped stores of sugar. Then see how the flow goes. I had 8 packages delivered April 10 this year. Stopped feeding the first week of May. All are doing well and have 4-6 frames of stores. If they don't gain enough, you can always feed again in the fall, but why use all that sugar in the Spring if they can forage enough for themselves. Also, if you continue to feed and they run out of space to put stores, the bees will backfill the brood nest and then swarm.
You won't be able to harvest anything from this hive for human consumption this year, as it will be condensed sugar rather than honey. But you can give them some space by doing as Rick suggested and freezing some of the capped sugar to give you space for empty bars.